A Study of the Effects of Pore Pressure the Strength and Deformability of Berea Sandstone in Triaxial Compression

摘要

Evidence is presented that pore pressures generated during loading can produce a measurable effect on the strength and deformability of the Berea Sandstone. While the E Modulus and axial strain at less than peak stress are apparently not sensitive to drainage condition, the axial strain at peak stress and the volumetric strain differ significantly between the undrained and drained states for comparable initial stress conditions. The dilatancy hardening phenomenon, found to be associated with the undrained state, causes the undrained strength to exceed the drained strength of backpressured specimens of sandstone at low initial effective stress conditions. The hardening, however, become less pronounced at higher initial effective stress states. A critical void ratio state, as defined for overconsolidated clay, appears to delineate the state of proximity of the mineral grains for which the dilatancy hardening phenomenon of the rock is completely suppressed. (Author)